1. Field of the Invention
The present invention concerns a substrate used for a magnetic disk by using a non-magnetic substrate such as glass, as well as a magnetic recording medium using such a substrate. More in particular, it relates to a substrate used for a magnetic disk capable of manufacturing a magnetic disk of excellent magnetic property and with high productivity, as well as a magnetic recording medium using such a substrate.
1. Description of the Prior Art
Generally, a glass substrate has been noted as a substrate used for a high density magnetic disk since the substrate has excellent surface smoothness, high hardness, and great deformation resistance, less surface defects, etc. (refer, for example, to Japanese Patent Laid Open Sho 49-122707 and Sho 52-18002).
A method of physically and/or chemically etching the surface of a glass substrate to form unevenness (or pits), thereby improving a contact characteristics (such as CSS property and, head static property) between a magnetic disk and a magnetic head has been known (for example, Japanese Patent Laid Open Sho 63-160010).
A method has also been known for forming pits on the surface of a glass substrate by means of spraying minute droplets of a solution of an organic metal compound thereby improving the contact characteristics (for example, in Japanese Patent Laid Open Sho 63-160014).
Further, a method has also been known for forming a pit forming layer made of Al on a glass substrate thereby improving the contact characteristics (Japanese Patent Laid Open Sho 62-256215).
When a magnetic disk is prepared by using a glass substrate formed with surface pits as described above, there has been problem that magnetic characteristics can not be attained as expected, although the contact characteristic can be improved.
In addition, there has been a problem that the method of forming the pits on the surface is complicated, or the method of etching the surface reduces the strength of the glass substrate or worsens the smoothness.
The method of using the organic metal compound has a merit of not reducing the strength or worsening the smoothness of the substrate since etching is not applied, but there has been a problem that a magnetic layer formed on the substrate often has a portion in which the performance is reduced, and only a substrate of low magnetic characteristic can be obtained.
Pits on the surface of the substrate with Al are formed because of a large cohesion energy of deposited metal (for example, Al) at the surface of the substrate at a high temperature. Then, when taking notice on the adhesion between the substrate and the deposited metal, since the cohesion energy between the atoms of the deposited metal is greater than the interaction between the substrate and the deposited metal, the adhesion between the deposited metal and the substrate is not generally strong. Therefore, when AL is continuously formed on the glass substrate, deterioration occurs at the Al/glass boundary due to the intense frictional force caused upon CSS rest. This is a problem which has to be solved before considering the usual problem of frictional coefficient due to friction between the head and the disk upon CSS test and it is a serious problem in view of the reliability of the magnetic disk.